This invention relates to a vehicle rear body structure configured to prevent a decrease in axial strengths of fixture bolts for rear-wheel dampers and to increase workability in tightening the dampers and a damper-mounting-portion reinforcing member together to damper mounting portions.
A conventional vehicle rear body structure is exemplified in FIGS. 9 and 10 hereof. In FIG. 9, wheel houses 101, 102 which accommodate left and right rear wheels are located at left and right sides of a rear floor panel 100. Damper mounting portions 103, 104 are located at routs or joints of the wheel houses 101, 102 for mounting left and right dampers 108, 109 to mitigate impacts or shocks transmitted from the rear wheels and to support the rear wheels. A reinforcement bar 105 serving as a damper-mounting-portion reinforcing member is arranged to extend between the damper mounting portions 103, 104 to allow the damper mounting portions 103, 104 to have increased rigidity. Reference numeral 107 designates a concave section for storing a spare tire. The reinforcement bar 105 is comprised of terminal metal fixtures 111, 112 secured to the damper mounting portions 103, 104, respectively, and a bar 113 unitarily coupled to the terminal metal fixtures 111, 112.
As shown in FIG. 10, both ends of the reinforcement bar 105 are tightened to the damper mounting portions 103, 104 together with the dampers. The terminal metal fixtures 111, 112 of the reinforcement bar 105 have pluralities of bolt insertion bores 114, 115, respectively, fitting a plurality of bolts 116 provided at upper distal ends of respective dampers into associated mounting bores, not shown, which are formed in the damper mounting portions 103, 104, upward from a rear side to allow the bolts 116 to pass through the bolt insertion bores 114, 115 of the terminal metal fixtures 111, 112, respectively, permits a nut, not shown, to be screwed onto each of the bolts 116.
Since the reinforcement bar 105 has mounting pitches P1, P2 (i.e., distances between bolts 116, 116 of the left and right dampers) which are substantially equal to a distance between the left and right wheels, such a structure suffers from an issue of increased manufacturing errors in the distance between the bolt insertion bore 114 and the bolt insertion bore 115. In order to absorb the manufacturing errors, the insertion bores 114, 114 for either ones of the left and right bolts are formed in elongated apertures.
Thus, the presence of the bolt insertion bore 114 formed in the elongated aperture causes a seating surface, which bears a nut to be screwed onto the bolt 116, to have a decreased surface area with a resultant increase in surface pressure acting on the seating surface when rotating the nut to be tightened with a given tightening torque. It seems that excessively higher the surface pressure of the seating surface, the lower will be the axial strength of the bolt due to deformation in the seating surface.
When tightening both the dampers 108, 109 and the reinforcement bar 105 together to the damper mounting portions 103, 104, mounting work must be initially carried out for mounting the terminal metal fixture 111 of the reinforcement bar 105 together with the dampers 108, 109 in an unsteady condition wherein the terminal metal fixture 112 of the reinforcement bar 105 is merely placed on the one-side damper mounting portion 104. This results in displacement of the terminal fixture 111 during the mounting operation to cause troublesome work in mounting the terminal metal fixture 111, resulting in deteriorated workability.
It is therefore an object of the present invention to provide an improved vehicle rear body structure which suppresses deterioration in axial strength of mounting bolts for rear-wheel dampers while providing improved workability in tightening both dampers and a damper-mounting-portion reinforcing member to damper mounting portions.
According to an aspect of the present invention, there is provided a vehicle rear body structure which comprises left and right damper mounting portions for mounting left and right dampers, which mitigate impacts transmitted from left and right rear wheels, to a vehicle body, respectively, a floor cross member disposed in the vicinity of the left and right damper mounting portions, and left and right gussets for coupling the left and right damper mounting portions and the floor cross member with respect to one another for reinforcing the left and right damper mounting portions.
With such a vehicle rear body structure, the presence of a structure wherein the left and right damper mounting portions are connected to the floor cross member at areas in the vicinity of the damper mounting portions via the left and right gussets enables the left and right damper mounting portions to have increased rigidity while shortening the mounting pitch, according to the present invention, to a lower value than that of the reinforcement bar employed in the conventional practice, resulting in a decrease in errors in the mounting pitches. Consequently, for example, when tightening the dampers and the gussets together to the damper mounting portions, there is no need for the bores formed in the gussets to pass the mounting bolts, formed at the upper portions of the dampers, to be formed in a larger size than that of an outer diameter of the mounting bolt of the damper, enabling the seating surface of the gusset which bears the nut to be screwed onto the mounting bolt to have an increased surface area. Accordingly, it is possible to preclude a decrease in the axial strength of the mounting bolt of the damper even when increasing the tightening torque of the nut discussed above.
Further, the damper and the gusset can be tightened together at the damper mounting portion under a condition where the gusset is mounted to the floor cross member, resulting in am improvement in the workability while enabling a productivity to be improved.
In the vehicle body structure arranged in accordance with the present invention, connecting the above left and right gussets with the rod enables the rigidity of the left and right damper mounting portions to be further improved with favorable results.